The influence of primary and subsequent limb amputation on the overall rate of limb amputation in Saskatchewan, Canada, 2006-2019: a population-based study

Background: Understanding trends in limb amputation (LA) can provide insight into the prevention and optimization of health care delivery. We examine the influence of primary (first report) and subsequent (multiple reports) limb amputation on the overall (all reports) rate of limb amputation in Saskatchewan considering amputation level.

Methods: Hospital discharged data associated with LA from 2006 to 2019 and population estimates in Saskatchewan were used. LA cases were grouped based on overall, primary, and subsequent LA and further divided by level into major (through/above the ankle/wrist) and minor (below the ankle/wrist). Incidence rates were calculated using LA cases as the numerator and resident population as the denominator. Joinpoint and negative binomial were used to analyze the trends. In addition, the top three amputation predisposing factors (APF) were described by LA groups.

Results: The rate of overall LA and primary LA remained stable (AAPC - 0.9 [95% CI - 3.9 to 2.3]) and (AAPC -1.9 [95% CI -4.2 to 0.4]) respectively, while the rate of subsequent LA increased 3.2% (AAPC 3.2 [95% CI 3.1 to 9.9]) over the 14-year study period. The rate of overall major LA declined 4.6% (AAPC - 4.6 [95% CI -7.3 to -1.7]) and was largely driven by the 5.9% decline in the rate of primary major LA (AAPC - 5.9 [95% CI - 11.3 to -0.2]). Subsequent major LA remained stable over the study period (AAPC -0.4 [95% CI - 6.8 to 6.5]). In contrast, the overall rate of minor LA increased 2.0% (AAPC 2.0 [95% CI 1.0 to 2.9]) over the study period which was largely driven by a 9.6% increase in the rate of subsequent minor LA (AAPC 9.6 [95% CI 4.9 to 14.4]). Primary minor LA rates remained stable over the study period (AAPC 0.6 [95% CI - 0.2 to 1.5]). The study cohorts were 1.3-fold greater risk of minor LA than major LA. Diabetes mellitus (DM) was the leading APF representing 72.8% of the cohort followed by peripheral vascular disease (PVD) and trauma with 17.1 and 10.1% respectively. Most (86.7%) of subsequent LA were performed on people with DM.

Conclusions: Overall LA rates remained stable over the study period with declining rates of major LA countered by rising rates of minor LA. Minor LA exceeded major LA with the largest rate increase identified in subsequent minor LA. Diabetes was the greatest APF for all LA groups. This rising rate of more frequent and repeated minor LA may reflect changing intervention strategies implemented to maintain limb function. The importance of long-term surveillance to understand rates of major and minor LA considering primary and subsequent intervention is an important step to evaluate and initiate prevention and limb loss management programs.